Definition of Normalcy
by nine worlds apart
Summary: But he must be as embarrassed as she was. They were almost siblings after all; and to find your sister doing...that...had to rank off-the-charts on every embarrassment scale. Derek/Casey


**Author's Note:** The Life with Derek fandom's a little inactive now which is sad :(

Well, this contribution's nothing much, but I hope others soon join back in. Take heed of the rating, kidlets.

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"You're doing it wrong."

She hastily withdrew her hand from beneath the covers and glared at the boy slouching by her open door. Or glared at the sheet covering her, because her heart was pumping excessive blood suddenly, and had increased the weight of her head, making it impossible for her to look up. Obviously.

Why was he at home, anyway? Or at her door for that matter. Which she had definitely locked. _Definitely. _There was no way she'd have been doing…what she had been doing had she known the door was-

"I'm not doing anything," she said, as her voice threatened to desert her, "I'm just…sleeping. You're completely wrong about whatever you're thinking. Not that there's anything new there, since I've never known you to _not_ be completely wrong about whatever you're thinking and I've always doubted your sanity and sensibility and morality and…_could you stop staring at me._"

"Casey, Casey, Casey," he sighed in mock exasperation, "Worst. Liar. Ever. Twitching covers is always a sure shot give-away."

His all too familiar triple repetition of her name made something jump low in her stomach and almost against her will she glanced up at a pair of familiar brown eyes, darker than she remembered and looking at her in a way that was definitely breaking laws over a lot of places in the world.

His face suddenly broke out into an impish grin as he looked at her fingers, which were suspiciously wet. It made her want to find a nice cheerful greensland, with a nice babbling well to jump into, because, oh god, he _knew._

She buried her heated face in her pillow, mortified, "Go away, Derek."

She heard her door close and sighed a little in relief, she hadn't expected him to do what she said. But he had to be as embarrassed as she was; they were almost siblings after all. And to find your sister doing…that had to rank off-the-charts on the embarrassment scale.

She looked up from the pillow… and shrieked. He still stood there, his arms crossed, leaning against her closed door and…still _there_.

"_Derek_. Why did you lock the door? _Go away_, you jerk."

She was horrified at the slight whiny note in her voice, a sure indication that she was going to cry. And she couldn't cry in front of him on top of everything else.

"Casey," she realized with a start that he'd adopted his Marti-tone, "I can't believe I'm saying this but it's _okay_, okay? It must be the most normal thing I've ever known you to do. You might even be a closer relation to the human race than I'd initially realized…but you're still doing it wrong."

"I am not." It was pointless pretending ignorance, "and how would _you_ know? You're not a girl. You wouldn't know how girls do it."

She realized the imbecility of the question as soon as she'd closed her mouth. And by his look of extreme amusement it was obvious they were perfectly in sync in their thought-processes. Which, more than anything else, was indicative of her degraded mental state.

"Contrary to what you appear to think…I do have…er…working knowledge of the female body actually," he said, making her hand itch to slap the smug look away from his face. How dare he think he knew more about this than she did?

"I'm doing it perfectly right, thank you very much," she snapped, "feel free to open the door and leave in the next five seconds."

He stayed. Big surprise.

"I feel it's my duty," he said, "I don't think it'd been fair to leave you like this, frustrated and even more uptight than usual. Actually, I don't think it would fair to the rest of humanity to have to deal with you in this state."

He couldn't possibly- what the _hell_- how could they- .

"No way," she tightened the sheet around herself in an unconscious defensive gesture, "No freaking way. It's probably _illegal_, you moron. I'll be in jail before I've even set a foot at Queen's, and we're siblings, how _sick _would you have to be…"

"Just, for the sake of argument," he said politely, dangerously, "what exactly do you think I'm proposing?"

She felt her face heat up again and cursed her traitorous blood-pumping organ, mumbling incoherently about _obviously _and _purely physical _and _on pretext of helping _and more in the same vein.

"You're insane," he said, interrupting her as she'd begun on _siblings _for the fifth time, "if you think, I'd ever do anything that involved touching you without the aid of a fifteen feet pole."

"Then what," she asked suspiciously. This was Derek. Duh.

"You continue doing what you were doing and I'll guide you along the way. Think of it as a free tutorial, courtesy your… big brother."

"I'm not doing it wrong," she said defiantly.

"We'll soon see that, won't we," he countered.

She moved her hand back under the sheet, under her skirt. He loudly cleared his throat, and she looked back at him, annoyed, "What now."

"My X-Ray vision is acting up today," he said politely, "I think it's because Nora's forgotten to wash my red underwear and blue bodysuit. So if you could just take off that sheet."

And that's when it hit her. He was going to _watch. _While she…touched. And she felt almost dirty as the heat pooled between her legs, and it was with a sickening thud of her heart that she realized that she was more turned on than she'd ever been with Truman.

She pulled off the sheet without argument. At least that way she could pretend that she would have totally been able to resist had she tried.

Her eyes were almost magnetically drawn to his and she slipped a finger inside the elastic of her soaked panties, and as she saw his gaze fixed on her she had a sudden urge to pull down her hiked-up skirt and hide her hand…or to pull it off completely. She wasn't sure which.

Her finger encountered wetness and her breathing grew labored. She ran her finger gently over her clit, and then pressed down, teasing herself.

"You're doing fine," he said in a monotone, and he really shouldn't have been able to talk normally even at this point. That was unfair.

She slipped a finger inside and arched her back slightly, and she heard his breath hitch a little. It strangely didn't make her feel like she'd won. She was a girl, albeit his almost-sister and any guy would react when a girl was…it wasn't _her_. The thought made her feel strangely disconsolate.

She added another finger, and bit back a groan as a familiar light-headedness engulfed her and she lost track of everything else around. Like him. She wasn't thinking of him at all. She so totally wasn't.

"Rise up a little," he said, his voice almost in that sphere of huskiness that stupid romantic movies thought was the only one fitting their stupid male leads.

"W-hat," she said, almost strangled, chokingly.

"Your body, Casey," he said quietly, "raise it from the bed a little. It'll help-"

She was about to argue when she realized that she didn't have the breath to do it and he'd said her name. Not that that mattered at all, but it added a…personal feel to the…tutorial. Which was always a good thing in any class, of course. She was a good student, an all 'A' student, so she knew that.

This time, she couldn't hold back a low moan as her fingers hit a bundle of nerves, and she'd never known her body could bear the pleasure. She wanted to stop because it almost hurt- burnt, but she was glad her fingers and Derek's eyes were impervious to all claims of sanity.

Her hand drifted upward of its own accord and she pulled it back down forcibly because she couldn't do _that_. It was completely personal and she needed to have _some _self-respect left after this incident, besides-

"Touch yourself," he whispered, breaking her inner monologue and sending her head spinning, "go ahead, touch, it feels good."

Her other hand, as if tuned to his instructions, slipped inside her bra. Her fingers on her hard nipples sending jolts of pleasure throughout her body. She ran her hand down her body, every nerve-ending responding to her searching tips and she knew she was close.

"Tur-n aro-und," she gasped. This was too private. And it meant a lot more that an indiscretion in her room with her family out. "Turn around, _please_, Derek."

His harsh breathing mingled with hers and suddenly his hand was on hers, almost on her skin. She hadn't even known he was so close, she realized, indignant. Almost.

And she couldn't help it, with a shuddering gasp she came.

She rode out the afterwaves and then pulled her hand out. Steadily looking at the print of the sheet and nowhere else.

"How do you taste," he asked, almost apathetically. And if his eyes hadn't been so dark she'd never have managed it.

"Weird," she said, sucking a finger, her face wrinkling.

And before she even realized, her finger was in his mouth and her heart was racing towards an attack.

"Yeah," he said, "weird."

But he still licked her other fingers and her knuckles turned white with her death grip over the sheet.

"I told you I was doing fine," she snapped, testing whether she could still string words together to make an almost-coherent sentence.

He looked at her, "I think it's a B."

"A… B," she squeaked in disbelief, "are you _kidding _me. That was so an A. An A+ in fact. You…you…_moron_…"

He shook his head sadly, in a faintly recognizable gesture, "Casey, Casey, Casey. You're going to need a lot of practice to get it up to an A. Your performance simply isn't up to the mark."

She was speechless with indignation.

"Tomorrow," he said, walking out, his hands clenched "my room. And kindly take off all your clothes next time. They're an impediment to observation."

And it's not like she'd expected anything else. At all. Because this was Derek. And Derek was never anything short of being Derek. And it'd always been Derek and…

It would always be Derek.

And anyway, she was an all-A student and she'd be damned if _Derek _was going to spoil her perfect record.


End file.
